Many systems use secondary power sources to maintain power when an event occurs, such as a power outage. For example, in a telecommunication environment equipment may be connected to backup batteries in the event that a primary power source is inoperable. These systems often switch to a secondary power source in an abrupt manner through a switch (e.g., contactor), which causes an instantaneous change in voltage to the system. Due to a difference in voltage levels of the secondary and primary power sources, the instantaneous change causes unwanted effects, such as voltage spikes and arcing, often damaging or resetting the system.